1. Field of the Invention
The present invention is generally related to a marine propulsion system and, more particularly, to a propulsion system that circulates cooling water through water jackets of its exhaust elbows in a manner that reduces the affected surface area in thermal communication with cooling water from a body of water so that condensation of water vapor entrained in the exhaust gas stream is reduced.
2. Background
Those skilled in the art of marine propulsion systems are familiar with various techniques used to conduct exhaust gas away from an internal combustion engine and emit the exhaust gas at a location behind a watercraft. In some applications, the exhaust gas is directed to flow through a marine drive unit and through the central opening of a propeller. In other applications, exhaust gas can be directed to flow through outlets above the surface of a body of water in which the marine vessel is operated. Regardless of the particular routing system used to conduct the flow of exhaust gas to a location behind the watercraft, the vast majority of marine propulsion systems collect the exhaust from the cylinders of an engine, in a manifold structure of some type, and then direct the exhaust gas through an elbow that is connected to one or more exhaust pipes. Typically, in V-type engines, two manifolds and two elbows are used.
U.S. Pat. No. 3,696,620, which issued to Pace on Oct. 10, 1972, describes a marine engine water cooling device. Improved water jacketed manifolds and water cooling systems for marine engines are described. Water circulation through the manifold water jacket is provided through an apertured pipe which extends through the jacket.
U.S. Pat. No. 3,759,041, which issued to North et al. on Sep. 18, 1973, discloses an exhaust water separator for marine engines. Arcuate exhaust elbows are provided which force cooling water in the exhaust to the outside by centrifugal action. This water is removed and expelled through the transom.
U.S. Pat. No. 3,780,712, which issued to Pace on Dec. 25, 1973, describes marine engine cooling. Heated water which is circulated through an engine cooling system for cooling purpose is mixed in the improved engine exhaust manifold water jacket with raw, relatively cool water to controllably cool the manifold and avoid condensing water from the exhaust gases flowing through the exhaust manifold.
U.S. Pat. No. 4,573,318, which issued to Entringer et al. on Mar. 4, 1986, discloses an exhaust elbow for a marine propulsion system. The exhaust elbow has an intake exhaust passage extending upwardly from the engine and communicating through a bend with a discharge exhaust passage, and a water jacket having pockets around the exhaust passages for cooling the latter. A central channel extends longitudinally along the exterior of the exhaust passages to guide water there along to the end of the discharge exhaust passage to mix with exhaust thereat. The central channel has a pair of sidewalls extending longitudinally and laterally tapered away from each other at the outer end of the discharge exhaust passage to create an outward draw from the central channel to minimize break-up of longitudinally outward water flow and maintain the end tip of the discharge exhaust passage dry and prevent water ingestion and creeping back into the discharge exhaust passage due to pulsations of the engine. Dam and port structure is also provided enabling faster heating of the exhaust passage and in turn minimizing condensation within the elbow which may otherwise ingest back into the engine.
U.S. Pat. No. 4,845,945, which issued to Widmer et al. on Jul. 11, 1989, discloses an exhaust elbow trough. A water jacketed exhaust elbow for a marine propulsion system includes an intake exhaust passage communicating with a discharge exhaust passage, a water jacket around the exhaust passages, and a trough member extending longitudinally along the water channel along the exterior of the discharge exhaust passage to guide water therealong to mix with exhaust at the end of the discharge exhaust passage. The trough member extends beyond the end tip of the discharge exhaust passage and has a sharp edge providing a clean parting surface for the coolant water and preventing ingestion of water back into the discharge exhaust passage.
U.S. Pat. No. 4,866,934, which issued to Lindstedt on Sep. 19, 1989, discloses a marine drive exhaust system with shaped O-ring seals. The exhaust system is provided with resilient, shaped rubber O-ring seals between facing surfaces of the exhaust manifold and exhaust elbow, and the facing surfaces of the exhaust elbow and the exhaust pipe. Each of the shaped O-ring seals has an inner peripheral rib extending peripherally around the exhaust passage and generally conforming to the shape thereof and being spaced laterally between the exhaust passage and the peripheral water passage. Each of the shaped O-ring seals has an outer peripheral rib extending peripherally around the water passages and spaced laterally outward of the inner rib by a gap through which the water passages extend.
U.S. Pat. No. 4,977,741, which issued to Lulloff et al. on Dec. 18, 1990, discloses a combination exhaust manifold and elbow for marine propulsion systems. A combination exhaust manifold and exhaust elbow for an internal combustion engine includes an exhaust cavity for receiving exhaust from the engine, an exhaust passage leaving from the exhaust cavity, and an exhaust discharge outlet. A first water jacket is provided around the exhaust cavity and a second water jacket is provided around the exhaust discharge passage. A dam is provided between the first and second water jackets, having a passage therein for allowing fluid communication between the first and second water jackets. A warm water inlet is provided in the first water jacket around the exhaust cavity for receiving cooling water which has been warmed by the engine, and which flow is controlled by a temperature sensitive thermostat. A cold water inlet is provided adjacent the discharge exhaust passage. The cold water inlet is disposed either upstream or downstream of the dam adjacent the exhaust passage, and allows cold bypass water to be discharged without the necessity of the cold water flowing through the entire assembly, so as to prevent moisture from condensing out of the exhaust in the exhaust cavity.
U.S. Pat. No. 4,991,546, which issued to Yoshimura on Feb. 12, 1991, describes a cooling device for a boat engine. A number of embodiments of cooling systems for internal combustion engines powering marine watercraft are described. The engine coolant jacket delivers its coolant to an exhaust manifold cooling jacket adjacent the inlet end of the exhaust manifold. Coolant is delivered from the exhaust manifold cooling jacket to a further cooling jacket around the inlet portion of an exhaust elbow. In one embodiment, a cooling jacket system is provided for the engine cooling jacket, exhaust manifold cooling jacket and the elbow cooling jacket. In another embodiment, the system discharges coolant back to the body of water in which the watercraft is operating through a further cooling jacket of the exhaust elbow that communicates with its discharge end.
U.S. Pat. No. 5,109,668, which issued to Lindstedt on May 5, 1992, discloses a marine exhaust manifold and elbow. An exhaust assembly includes a manifold portion, an elbow portion, a water jacket portion, and exhaust runner walls, providing a smooth continuous transition of exhaust gas flow from intake exhaust passages in the manifold portion to transfer exhaust passages in the elbow portion around a bend to a discharge exhaust passage, minimizing turbulent flow of exhaust through the manifold portion and elbow portion.
U.S. Pat. No. 5,644,914, which issued to Deavers et al. on Jul. 8, 1997, discloses an exhaust pressure pulsation control apparatus for a marine propulsion system. It has a front ring and a reflector disk located downstream of the front ring. There is a space between the front ring and the reflector disk that is sufficiently large so that the mixture of water and water cooled exhaust passing through the apparatus does not have a significant pressure drop. The apparatus attenuates pressure pulsations in the exhaust system, thereby significantly reducing water ingestion through the exhaust system into the engine. The apparatus does not create significant exhaust back pressure, and typically increases engine maximum power output.
U.S. Pat. No. 6,290,558, which issued to Erickson on Sep. 18, 2001, discloses an exhaust elbow with a water trap for a marine propulsion system. The water trap section defines a water collection cavity. Within the water trap section, a barrier extends downward into the water collection cavity to define first and second exhaust passages. When water begins to collect in the water collection cavity, the cross-sectional area of the exhaust passage is reduced and the velocity of exhaust gases passing through the exhaust passage is increased. The water collection cavity is shaped to be easily cleared when exhaust gas pressure increases as the engine speed increases.
U.S. Pat. No. 6,478,645, which issued to Allbright et al. on Nov. 12, 2002, describes a moisture migration inhibitor for wet marine exhaust. A moisture inhibitor system for wet exhaust as utilized in marine applications, such as boats and other watercraft, is described. The preferred embodiment contemplates an exhaust manifold having an inner exhaust passage which has situated therein a collection barrier or raised pocket situated to collect moisture migrating from the exhaust port, generally at the stern of the vessel. The collection pocket is heated by the exhaust stream and is formed to collect and retain the migrating moisture while simultaneously the heated walls of the collection barrier evaporate the collected moisture forming moisture vapor which moisture vapor is urged through the exhaust passage and the exhaust port, where it leaves the system.
U.S. Pat. No. 6,582,263, which issued to Jaeger et al. on Jun. 24, 2003, discloses a marine exhaust elbow structure with enhanced water drain capability. The elbow is provided with a stainless steel tube within a water outlet opening to assure that a drain opening remains open even when the exhaust elbow is exposed to a corrosive environment. Since cast iron tends to expand in volume as a result of corrosion of its surface areas, water outlet openings intended to perform a draining function can be partially or fully closed as a result of corrosion. The insertion of a stainless steel tube in one or more water outlet openings of an exhaust elbow assures that an internal water cavity of the elbow can drain when the associated internal combustion engine is turned off, thereby minimizing the possibility of freeze damage to the exhaust components.
U.S. Pat. No. 6,652,337, which issued to Logan et al. on Nov. 25, 2003, discloses an exhaust system for a marine propulsion engine. A relationship between the exhaust passages and coolant passages of an exhaust manifold and exhaust elbow serves to maintain the joint of the exhaust passage at a higher temperature than would be possible with known exhaust manifolds and exhaust elbows. By providing a space between surfaces of a raised exhaust portion of the components and surfaces of the raised coolant portions of the exhaust system, leakage from the coolant conduit to the exhaust cavities is avoided.
U.S. Pat. No. 6,800,004, which issued to White et al. on Oct. 5, 2004, discloses a marine exhaust cooling system. It uses an orifice to distribute liquid coolant flow between two alternative and parallel paths. One coolant path passes through a generally horizontal portion of an exhaust elbow and the other coolant path passes through the orifice and directly to a vertical riser of the exhaust elbow. The ratio of flow between the two paths changes as a function of engine speed because of the operation of the orifice which provides increased resistance to flow as a function of increased pressure drop across the orifice.
U.S. Pat. No. 6,929,520, which issued to Hughes et al. on Aug. 16, 2005, discloses a cooling method for a marine propulsion system. It directs a portion of a recirculating stream of cooling water to a first portion of an exhaust manifold so that the cooling jacket of the exhaust manifold can be maintained in a filled condition. Water flows upwardly through the cooling jacket and exits through a port in the exhaust manifold back into a recirculating stream of cooling water that passes through a recirculation pump, the cooling passage of an engine, and a cavity of a thermostat housing.
U.S. Pat. No. 7,427,222, which issued to Auck et al. on Sep. 23, 2008, describes a reversion control device for a watercraft exhaust system. The device is a reversion control device including a housing for a stationary vane and a flapper. In one example, the housing includes an expansion chamber to house the stationary vane and the flapper.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Marine propulsion systems normally draw water from a body of water in which the marine vessel is operating and direct the water to flow through various devices in order to remove heat from heat producing components. The temperature of the water drawn from the body of water can vary significantly, depending on the season of the year and the geographical region where the body of water is located. The exhaust gases produced by the engine contain water vapor. Exposing the stream of exhaust gas to low temperatures caused by the use of cold cooling water can result in condensation within the exhaust conduits of the system. The formation of condensation can be significantly disadvantageous, as described within numerous ones of the patents cited above. Among these disadvantages is the potential flow of condensed water back toward the exhaust ports of the engines' cylinders. In addition, if the engine is provided with one or more catalyst devices, the condensed water can possibly flow toward and in contact with the catalyst components. It would therefore be significantly advantageous if the creation of condensed water vapor in the exhaust conduits could be reduced or eliminated.